In Argentina there is a black market for USD which means tourists who know this can use USD to their advantage. On the legal market you currently get 5.7 pesos to $1, but on the black market you get 9.6 pesos right now. I knew this before I left Melbourne but was worried about where I could exchange my money and if my lack of Spanish would cause me to get ripped off (apparently fake notes can be common). I was pleasantly surprised however, when my hostel could exchange my dollars for pesos, at the exchange rate of a satisfactory 8 pesos. Note, you can not get USD out in Argentina, so you have to bring it in to get the good exchange rate.

Although I used this black market to my advantage I was curious to know why such a market existed.

In Argentina inflation is high. Last year it was 25%. This means no one puts money in banks. Its a cash under their mattresses situation. USD gives them a kind of security in their very volatile economy. This need has created the black market, the dolar blue.